Apparatus for producing flexible styrene polymers



Jan. 28, 1964 a. KRACHT 3,119,147

APPARATUS FOR PRODUCING FLEXIBLE STYRENE POLYMERS Filed Aug. 21. 1961 CON m; IJSATB v .v .v .u................

United States Patent 3,119,147 APPARATUS F922 PRQDUCKNG FLEXIBLE STYREIJE P@LYMER Gerhart Kracht, Beaver, Pa, assignor to Koppers Company, inc, a corporation of Delaware Filed Aug. 21, 1961, Ser. No. 132,955 2 Claims. (Cl. 18-1) This invention relates to apparatus for producing flexible foamed styrene polymers.

Co-pending application, Serial No. 859,626, and now abandoned, filed December lS, 1959, by T. V. Roberts and R. H. Immel and assigned to the 'assignee of this invention, describes a process for producing resilient polystyrene foam. According to that application, a sheet of rigid polystyrene foam is subjected to compressive forces until its original thickness is reduced to at least 80 percent and thereafter the compressive forces released. This process has been carried out hereto-fore by the use of presses which increase the density of the final product.

In accordance with this invention, sheets of fomed styrene polymer are rendered flexible and their density is decreased by passing the sheet through crushing rolls, then subjecting the sheets to steam pressure to re-expand the sheet, again passing the sheet through crushing rolls and thereafter re-expanding the foam at atmospheric pressure with steam.

This invention contemplates novel apparatus for producing flexible foamed styrene polymers which comprises a housing that is divided into three chambers whereby air may be introduced into one chamber for cooling and steam may be injected into the other chambers for heating, the steam chambers being closed by pairs of coacting crushing rollers which include an adjustment for varying the crushing force applied by the rollers whereby a sheet of foamed styrene polymer may be passed through the rollers and be crushed thereby, then pass through steam chambers for heating and through an air chamber for cooling.

T he above and other objects and novel features of this invention will appear more fully from the detailed description when the same is read in conjunction with t e accompanying drawing. It is to be expressly understood, however, that the drawing is not intended to be a definition of the invention, but is for the purpose of illustration only.

The single sheet of drawing illustrates partially in crosssection an embodiment of the novel apparatus of this invention.

Turning now to the drawing: the housing 11 is divided by plates 13 and 14 and crushing rolls 31, 32', 54-, and 65 into chambers A, B, and C, plates 13 and 14- terminate in resilient members :16 which by coaction serve to seal one chamber from the other. Rollers 3d, 3-2 and 6d, serve to seal chamber C. An inlet 2.7 is provided for introducing air into chamber A and an outlet 25 provided for removal of air from chamber A, an inlet IQ is provided for the injection of steam into chamber B and a check valve and line 17 is provided for the removal of condensate from chamber B, an inlet 21 is provided for the injection of steam into chamber C and a check valve and line 23 is provided for the removal of condensate from chamber C.

Chamber B is sealed by two pairs of coacting rollers 31 and 32 and 64 65, these rollers are mounted in seals 35 and 36, and 68, ea, springs 33, 3*)", 72, and 73 provide the compressive force on rollers 31, 32, 64' and 65. This compressive force is adjustable by way of screws 45 4-1, 7 4- and 76. Idle rollers 43 in chambers A, B and C provide support for the sheet of foamed styrene polymer.

Sheets of foamed styrene polymer are readily available commercially. Such sheets can also be made conveniently by subjecting an expandable styrene polymer, that "ice is, one having from 5 to 15 percent of a volatile hydrocarbon incorporated therein, to heat whereupon the polymer particles expand and fuse together to form a foamed structure. Such particles are sold commercially, for example, under the trademark Dylite and may be made into sheets in accordance with the process described in Stastny Patent No. 2,779,062. These sheets may then be sliced to thinner sheets of the desired thickness.

To illustrate the operation of the apparatus of this invention, a large cylinder 7 of foamed styrene polymer is produced by partially filling a cylindrical mold with expandable styrene polymer particles (Dylite). The mold and foam particles are then heated by steam and cooled, the foamed styrene polymer cylinder 7 is then removed from the mold. This cylinder 7 is then tangentially cut by knife 8 into sheets having the desired thickness. The sheet 9 is then passed through rollers 31, '32. and crushed to about one-half its original thickness. It then passes into chamber C where the sheet is subjected to steam at a pressure of from 7 to 15 psig. Thereafter, the expanded foamed sheet is passed through crushing rollers 64, 65. Upon passing through rollers 64-, 65, the thickness of the sheet is reduced to about one-fourth the original thickness. The sheet is then passed through chamber B and subjected to steam at atmospheric pressure where it is re-expanded. Thereafter, the sheet is passed into chamber A where it is cooled. The sheet thus obtained is soft and flexible and is about one-half as dense as the original sheet.

As is evident from the foregoing, the final dimension of a sheet as Well as the degree of softness, flexibility, and resiliency can be controlled by controlling the length of heating time, degree of compression, and cooling time to which the sheet is subjected. The final density of the foam is also controlled by the above method.

The term styrene polymers includes homopolymers of styrene and copolymers of styrene that contain more than 50* percent and preferably more than percent by weight of styrene. Examples of monomers that may be copolymerized with the styrene monomer include the conjugated '1,'3-dienes, e.g., but-adiene, isoprene, etc., alpha, beta-unsaturated rnonocarboxylic acids and derivatives thereof, e.g., acrylic acid, methyl acrylate, ethyl acrylate, butyl acryl-ate, 2-ethylhexyl acrylate and the corresponding esters of methacrylic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, divinyl benzene, etc. Also included are blends of the styrene polymer with other polymers, such as, blends of styrene polymer with rubbery diene polymers or the analogous compositions obtained by dissolving a rubbery diene polymer in styrene monomer and subsequently polymerizing the mixture. All or a portion of the styrene may be replaced with its closely related homologues such as alphamethylstyrene, 0-, 111-, and p-ethylstyrenes, 0-, m, and p-methylstyrenes, 2,4-dimethylstyrene.

The foregoing provides a novel apparatus for producing sheets of foamed styrene polymer which are usable, for exmple, in packaging where high energy absorbing qualities are desired.

What is claimed:

1. Apparatus for producing flexible foamed styrene polymer sheets of low density comprising a housing and means for dividing said housing into an air chamber and two steam chambers, means for flowing air through said air chamber, and means for injecting steam into said steam chambers, said steam chambers including a pair of coacting rollers for closing said steam chambers whereby a sheet of foamed styrene polymer may be passed through said rollers to be crushed thereby, then into said steam chambers to be heated thereby and then into said air chamber to be cooled thereby.

3 4 2. The apparatus of claim 1, wherein an adjustment is 2,518,125 Crabbe et al. Aug. 8, 1950 provided for varying the crushing force of said rollers. 2,557,439 Kmentt June 19, 1951 2,797,201 Veatch et a1 June 25, 1957 References Cited in the file of this patent 2,861,046 Stastny Nov. 18, 1958 UNITED STATES PATENTS 5 3,082,774 Benton et al Mar. 22, 1963 2,433,094 Crowley Dec. 23, 1947 FOREIGN PATENTS 2,446,620 Swallow etal Aug. 10, 1948 837,714 Germany y 8, 1949 

1. APPARATUS FOR PRODUCING FLEXIBLE FOAMED STYRENE POLYMER SHEETS OF LOW DENSITY COMPRISING A HOUSING AND MEANS FOR DIVIDING SID HOUSING INTO AN AIR CHAMBER AND TWO STREAM CHAMBERS, MEANS FOR FLOWING AIR THROUGH SAID AIR CHAMBER, AND MEANS FOR INJECTING STEAM INTO SID STEAM CHAMBERS, SAID STEAM CHAMBERS INCLUDING A PAIR OF COACTING ROLLERS FOR CLOSING SAID STEAM CHAMBERS WHEREBY A SHEET OF FOAMED STYRENE POLYMER MAY BE PASSED THROUGH SAID ROLLERS TO BE CRUSHED THEREBY, THEN INTO SAID STEAM 